1. Field of the Invention
The present invention relates to an output power transmission device and to a motor with a speed reducing mechanism.
2. Description of Related Art
Conventionally, for example, a power window motor for opening and closing window glass of an automobile is constructed of a motor with a speed reducing mechanism, in which an output power transmission device (a speed reducing section) and a motor main body are integrated. The output power transmission device is constructed by meshing a worm shaft, which rotates due to drive of the motor main body, and a wheel gear (for example, refer to Patent document 1: Japanese Utility Model No. H6-69493). The output power transmission device has the worm shaft, the wheel gear meshed with the worm shaft, a transmission member and an output shaft (an intermediate wheel and a pinion in Patent document 1), the transmission member and the output shaft rotating integrally with the wheel gear. A damper as a buffer member is provided between the wheel gear and the output shaft. The damper contacts with the wheel gear and the output shaft in the axial direction and the rotation direction of the wheel gear, respectively. The damper functions to absorb a shock at the time when the worm shaft transmits the rotation to the output shaft. Thus, breakage of component parts of the output power transmission device such as the worm shaft is inhibited.
In such the output power transmission device, improvement of strength of the worm shaft and the like enables a structure that does not need the damper, thereby contributing to inhibition of increase of the number of the parts. However, if the damper is eliminated, it is anticipated that backlash arises between the wheel gear and the output shaft in the axial direction of the wheel gear due to a dimension error, an assembly error and the like. Thus, there is a room for improvement in this point.
Another example of power window motor for opening and closing window glass of an automobile (described in Patent document 2: JP-A-2001-343052) is constructed of a motor with a speed reducing mechanism, in which an output power transmission device (a speed reducing section) is integrated with a motor main body. The output power transmission device is constructed by meshing a worm shaft, which rotates due to drive of the motor main body, with a wheel gear. The output power transmission device is structured such that the rotation of the worm shaft is transmitted to an output shaft through the wheel gear and a metallic transmission member (a driving force output plate in Patent document 2) rotating integrally the wheel gear. The transmission member is attached to an axial end face of the wheel gear and functions to improve strength of the gear. A damper as a buffer member is provided between the wheel gear and the transmission member. The damper is interposed between the wheel gear and the transmission member in a direction of the rotation of the wheel gear and functions to absorb a shock at the time when the worm shaft transmits the rotation to the output shaft. Thus, breakage of component parts of the output power transmission device such as the worm shaft is inhibited.
However, in the above-described output power transmission device, the damper as the buffer member is provided as a separate member. Therefore, the number of the parts is large, and there is a room for improvement in this point.